1. Title of the Invention
The present invention relates to a synthetic resin introduction cannula used for introducing and indwelling a rod-like medical tool such as a catheter, a guide wire, or the like in a blood vessel, and a method of manufacturing the same.
2. Description of the Related Art
Conventionally, when a catheter is introduced and indwelled in a blood vessel, a flexible introduction cannula of a synthetic resin is used. More specifically, an introduction cannula is fitted on an inner cannula of a syringe so that the distal end of the inner cannula projects therefrom. The inner cannula is then pierced into a blood vessel until the distal end of the introduction cannula is inserted in the blood vessel. Then, the inner cannula is removed from the blood vessel while the introduction cannula is left in position. In this manner, a desired catheter is inserted in the introduction cannula while the introduction cannula is left in the blood vessel, and the distal end portion of the catheter is then inserted in the blood vessel. After the catheter is indwelled at a predetermined position in the blood vessel, the unnecessary introduction cannula is removed from the blood vessel. Preferably, the introduction cannula is also removed from the catheter. It is undesirable for sanitary reasons that the introduction cannula is left in the body after being removed from the blood vessel. In addition, the introduction cannula in this state disturbs the subsequent operations.
However, it is impossible to pull out the introduction cannula from the catheter since an extended portion such a connector of the catheter is present.
For this reason, some proposals for removing the used introduction cannula from the catheter have been made. For example, in one proposal, a slit is preformed in the longitudinal direction of the introduction cannula, and the introduction cannula is removed from the catheter through the slit.
In Japanese Patent Disclosure (Kokai) No. 56-11069, a pair of linear members of a single plastic material different from that of the remaining portion are formed in opposing portions in the radial direction of an introduction tube. The base portion of an introduction cannula is coupled to a fitting portion with an inner cannula hub with a slit, which is coupled to the linear members. The used introduction cannula is torn at the linear members to be split into two portions while gripping the fitting portion.
However, in the former method, the mechanical strength of the introduction cannula is decreased, resulting in poor operability. In addition, when a cannula is introduced into a blood vessel, blood may leak from the slit. In the latter method, the linear members are easily cracked upon post-machining, e.g., cutting, distal end machining, and the like of the introduction cannula or handling as a product. An introduction cannula with cracked linear members cannot be used, and, if used, blood leakage may occur.
In the introduction cannula having linear members for splitting the introduction cannula as described above, since the color of the strip members resembles that of the introduction cannula body, it is difficult to immediately confirm the positions of the strip members when they are removed from the introduction cannula body, resulting in cumbersome splitting operation of the introduction cannula.